In the fields of wireless communication and power management, various components can be implemented using semiconductor devices such as transistors. For example, in radio frequency (RF) communication, the RF front end is a generic term for the circuitry between an antenna and a digital baseband system and the RF front end may include multiple transistor-based components, such as switches and amplifiers, to name some examples. Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, such as silicon (Si), germanium (Ge), and gallium arsenide (GaAs), to name a few examples. A field-effect transistor (FET) is a semiconductor device that includes three terminals: a gate, a source, and a drain. A FET uses an electric field applied by the gate to control the electrical conductivity of a channel through which charge carriers (e.g., electrons or holes) flow from the source to the drain. Some FETs have a fourth terminal called, the body or substrate, which can be used to bias the transistor. A metal-oxide-semiconductor FET (MOSFET) is configured with an insulator between the gate and the body of the transistor, and MOSFETs are commonly used for amplifying or switching electronic signals. In some cases, MOSFETs include sidewall spacers (or so-called gate spacers) on either side of the gate that can help determine the channel length and can help with replacement gate processes, for example.
These and other features of the present embodiments will be understood better by reading the following detailed description, taken together with the figures herein described. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Furthermore, as will be appreciated, the figures are not necessarily drawn to scale or intended to limit the described embodiments to the specific configurations shown. For instance, while some figures generally indicate straight lines, right angles, and smooth surfaces, an actual implementation of the disclosed techniques may have less than perfect straight lines and right angles, and some features may have surface topography or otherwise be non-smooth, given real-world limitations of fabrication processes. In short, the figures are provided merely to show example structures.